Production of motor fuels by alkylation



April 25, 1950 s. H. M ALLISTER ETAL 2,505,644

PRODUCTION OF MOTOR FUELS BY ALKYLATION Original Filed Dec. 14, 1938[Zesisf'an .ms 6 V M Edwin F Eullard Eu, H'nair A'H'orneui Patented Apr.25, 1950 PRODUCTION OF MOTOR FUELS BY ALKYLATION Sumner H. McAllister,Lafayette, and Edwin F.

Bullard, Oakland, Calif., assignors to Shell Development Company, SanFrancisco, Calif., a

corporation of Delaware Original application December 14, 1938, SerialNo. 245,714. Divided and this application May 24, 1946, Serial No.671,988

8 Claims. 1

This invention relates to a low temperature process for reactingisoparaflins with olefins in the liquid phase in the presence ofcatalyst acid, particularly sulfuric acid, to form higher boilinghydrocarbons. It deals particularly with a new and more efficient methodfor carrying out such reactions in a continuous manner in whichundesirable side reactions may be minimized.

An important object to our invention is the provision of a continuousprocess for reacting isoparafiins with olefins in which the effectivelife of the catalyst acid is unusually long and its cost correspondinglylow. Another object of the process of our invention is to provide asimple method whereby a high ratio of isoparafiin to olefin may becontinuously maintained in the reaction zone and accumulation of olefinin the reactor avoided. Still another object of our invention is toprevent undesirable reactions of the olefin used, especially hydration,esterification and polymerization reactions. A further object of ournovel process is to reduce to a minimum the power required fordispersing the reactants in the catalyst acid while insuring complete,uniform and intimate dispersion. It is also an object of our inventionto provide a method of operation which makes practical high rates ofproduction per volume of reaction space.

The process of our invention provides an especially advantageous methodfor reacting lower boiling isoparaffins such as isobutane and isopentanewith normally gaseous olefins such as propylene, normal and/orisobutylenes to form paraffins which boil within the gasoline range andhave a high anti-knock value. It will be understood, however, that ournew reaction method is not limited to these specific reactions but mayadvantageously be used in the manufacture of other branched chainsaturated compounds by reacting saturated aliphatic hydrocarbons havinga hydrogen atom attached to a tertiary carbon atom, whether normallygaseous or liquid, such, for example, as 2-methy1 pentane, 2,3-dimethylbutane, 2,2,3-trimethyl butane, 3-ethy1 pentane, methylcyclopentane, orsuitable substitution products thereof such, for example, asmonochlorides corresponding thereto or the like, with the same or otherolefins. Olefins which may be reacted with such compounds in accordancewith the process of our invention include, in addition to propylene andthe butylenes, alpha and beta amylene, isopropylethylene, trimethylethylene, unsymmetrical methyl ethyl ethylene, isobutyl-ethylene,iso-octylenes, cyclopentene, cyclohexene, butadiene, cyclohexadiene, orthe corresponding unsaturated chlorides, and the like. The reactants maybe used in a pure state as a mixture of one or more isoparaffins withone or more olefins or as such mixtures containing other componentswhich may or may not be inert under the reaction conditions but whichare such that they do not interfere with the desired reaction betweenthe isoparafiin or isoparafiins and the olefin or olefins being reacted.Thus hydrogen, nitrogen, methane, ethane, propane, normal butane,tetramethyl methane, ethylene and the like, for example, may be present.Particularly advantageous sources of isoparaflins and olefins which maybe reacted in accordance with the process of our invention arehydrocarbons derived from petroleum, petroleum products, shale oils,coal peat, animal or vegetable oils or like carboniferous materials. Theisoparafilns and/or olefiins present in the starting material may be ofnatural occurrence, the result of catalytic dehydrogenation, cracking orother pyrogenetic treatment. Cracked petroleum distillates or specialiractions thereof, particularly hydrocarbon fractions consisting of, orpredominating in, hydrocarbons containing the same number of carbonatoms per molecule, may be used although non-isomeric mixtures are alsosuitable. Such hydrocarbon fractions or mixtures may advantageously besubjected to a polymerization treatment prior to their treatment inaccordance with the process of the present invention. For example, themixture may be first treated to interpolymerize tertiary olefins withsecondary olefins and the residual hydrocarbon containing isoparaifinand olefins, generally principally secondary olefin or olefins, used asstarting material for our process. Copending application Serial No.133,203 of Sumner H. McAllister, filed March 26, 1937, now United StatesPatent No. 2,174,247, describes an especially advantageous method forcarrying out such a preliminary interpolymerization step. Alternatively,tertiary olefin or olefins may be selectively polymerized in part orsubstantially quantitatively prior to carrying out the present processwith the residual isoparafiin and olefin content. United States PatentsNos. 1,938,177, 2,007,159 and 2,007,160 describe suitable methods forcarrying out the preliminary removal of tertiary olefins. Whatever thepreliminary polymerization treatment used, the present process may becarried out with the remaining isoparaffin whether or not the olefinpolymers are first separated therefrom.

While we do not wish to be limited to any particular theory with respectto the present invention, the following explanation of the process ofour invention will assist in making clear its method of operation and inexplaining the highly advantageous results attained. The isoparaffin isconsidered as the less reactive molecule and the olefin as the morereactive molecule involved in the process of our invention. In thepresence of an acid catalyst, such as sulfuric acid of at least 90%concentration or its equivalent, the olefin can be made to react withthe isoparamn. The reaction may be considered as taking place in theacid phase. The olefin can also readily react with the acid to formmonoor (ii-sulfates or alcohols or others or with other molecules of thesame or other olefins if present to form coor interpolymers. These sidereactions, particularly those of the olefin with the acid areundesirable not only because they reduce the yield of isoparafiinreaction products but also because they very seriously impair the lifeof the catalyst. Relatively small amounts of olefin are capable ofleading to rapid deterioration of the acid catalyst. Olefins areabsorbed by catalyst acids at enormously faster rates than areisoparaifins. For example, the rates of absorption of alpha and betabutylenes in 97% sulfuric acid at 25 C. are about 620 and 740 times,respectively, that of isobutane. This greatly increases the difilcultyof protecting the catalyst acid from undesirable olefin absorption. Wehave found, however, that the rate or absorption of olefin may bematerially reduced by proper dilution of the olefin and that it isparticularly desirable to dilute the olefin feed with the iscparaffin tobe used in the reaction as in this way longer cat,- alyst acid life ispossible. At the same time it, is highly advantageous to provideconditions. favorable for high rates of isoparafnn absorption, such asstrong acid solutions, and in particular by having large amounts ofisoparaffin, preferably in high concentration, present in the reac tionzone. Merely having an excess of isoparaffifin present is alone notsufiicient to insure a long catalyst life and provision should be madefor substantially complete reaction of the olefin in order that theremay be no accumulation of olefin in the system. We have discovered that,contrary to previously held ideas, the reaction between isoparafiins andolefins to form higher boiling saturated hydrocarbons can be made arelatively rapid one.

Based on these discoveries we have developed an efiicient, technicallypractical method for continuously reacting isoparaifins with olefinswhich gives long catalyst life and extremely high rates of productionper volume of reaction space while insuring high yields of uniformlyhigh quality products. In our process the ratio of isoparafiin to olefinin the reaction zone is advantageously maintained higher than that inthe feed. This more favorable reaction conditionis achieved by recyclinga part of the reacted mixture rich in isoparafiin, but substantiallyfree. from olefins, to mix with the feed as it enters the reactor. Inour preferred method of carrying out our process we advantageouslyoperate with twostages of dilution of the olefinic feed, first dilutingthe olefin feed stock with isoparafiimcontaining hydrocarbon beforebringing it intocontact with the catalyst acid and then adding thismixture to recycled reaction mixture of dispersed catalyst andisoparafiin containing hydrocarbon which is substantially olefin-free.In any case we prefer to operate with a high concentration of theisoparafiin which it is desired to react in contact with the catalystacid and present in excess over the olefin used. By this; method ofoperation and the proper adjust ment of contact time, acid strength,temperature and acid to hydrocarbon ratio complete reaction of theolefin is readily achieved and we find it feasible to so operate that inthe reactor proper the olefin concentration is so low that it is notmeasurable by existing analytical methods. To this end, it is highlyadvantageous to provide thorough, uniform, positive mixing of a smallamount of olefin in a large amount of isoparafiin so that no shortcircuiting or accumulation of olefin anywhere in the system takes place.

While other methods of operation may be used without departing from thespirit of our invention, the accompanying drawing illustrates,diagrammatically, one assembly of apparatus particularly suitable forlarge scale application of the process of our invention, in whichoptimum reaction conditions can be readily maintained. In the drawingpipe lines I and 2 are supply lines for isoparaffin and olefincontaining hydrocarbon, respectively, from sources not shown, which aremixed in line 3. The rate of feed of the resulting mixture may beregulated by adjustment of valve 4. In line 3 the isoparaifin and olefinfeed may be diluted with isoparafiin containing hydrocarbon introducedthrough lines 25 and/or 32. The feed from pipe 3 is introduced into line5 where it contacts recycled reaction mixture comprising catalyst acid,preferably sulfuric acid, and unreacted isoparaffin. It is highlydesirable that the mixing at this point be as thorough and rapid aspossible. Line 5 is communication with positive circulating means suchas pump 6 which passes a part of the mixture of hydrocarbon and catalystby lines I, 8 and 9 to a means for maintaining the mixture in adispersed condition until reaction is substantially complete which maytake the form of time tank It or the like. A branch line H leading tocooler 12 permits cooling sufiicient of the reaction mixture by indirectheat transfer to a suitable cooling medium, to bring the temperature ofthe entire mixture to the desired point after reintroduction of thecooled portion via line l3 connecting cooler l2 with line ii. The amountof reaction mixture circulated through the cooler instead of via line 3may be regulated by inserting a suitable resistance It which may takethe form of an orifice plate or the like in line B. The circulatingstream of reaction mixture passes by line 9 to a time tank 10 whichadvantageously may be equipped with perforated plates so spaced thatthey provide a degree of turbulence sufficient to maintain the desireddispersion of catalyst acid and hydrocarbon throughout the time ofresistance of the mixture in the tank although suitably packed towers orcoils of pipe of suitable diameter and length or other equivalent meansmay be used. From the time'tank 10 the reaction circulates by line l5 toline 5 where it again contacts incoming isoparaifin and olefin feed fromline 3. Before such contact, however, a side, stream is withdrawn byline 16 to means for separating immiscible liquids such as stratifier l!where stratification takes place and the upper, hydrocarbon layer isremoved through pipe line it. The lower, catalyst acid layer is returnedto the circulation system by line [9 connecting separator ll with line 5at a point on the down stream side or", and advantageously substantiallyremoved from, the point of con nection of feed inlet line 3; Theproportion of reaction mixture withdrawn to the separator is controlledby placing a definite resistance 23 in the recycle stream and by athrottle valve-22 in the line returning acid phase from the separator.It is helpful in the maintenance of the circulating pump stuifing box toallow this element to operate exclusively on hydrocarbon or on acidphase as it is diflicult to provide materials equally resistant to bothphases. Thus, a line 24 may be provided whereby a part of the stream ofacid from separator IT can be taken off and used to seal the stufiingbox of pump 6. Alternatively, hydrocarbons can be used by directing partor all of the feed from lines I and 2 to the pump stuffing box.

It is a feature of the process of our invention that the acid catalystused is preferably preconditioned before the start of the reaction bybeing first saturated with olefin-free hydrocarbon, preferablyhydrocarbon containing the isoparafiin to be used in the process. Tothis end, the apparatus, in starting operations, is first charged withisoparaffin containing hydrocarbons, free from olefins, and the requiredamount of catalyst acid, for example, sulfuric acid of 90% to 110%concentration, is then added. In general, a ratio of about 0.2 to about2 volumes of acid phase per volume of hydrocarbon phase may be used,although ratios of about 0.4 to about 1.2, such that the hydrocarbonconstitutes the continuous phase in the resulting dispersion, arepreferred as case of dispersion is facilitated thereby, but higher andlower ratios may be used; although excessively high acid ratios whichresult in too great a decrease in the volume of hydrocarbon in therecycle stream are undesirable. With the dispersion of sulfuric acid andisoparaffin hydrocarbon flowing uniformly through the system, valve 4 isopened and the olefinic feed, preferably containing at least an equalmolecular amount of isoparaffin and preferably containing an excess ofisoparafiin, most preferably at least 3 molecules of isoparafiin permolecule of olefin is admitted through line 3. The.

rate of feed of reactants is preferably so adjusted with respect to therate of flow of recycle stream through line 5, that the ratio ofisoparaf-, fin to olefin at the point of contact of acid and olefin isof the order of at least 20 to l and more preferably is at least 50to 1. Ratios of about 100 to about 400 to 1 and higher may be used; itbeing only undesirable to employ such high ratios that the plantcapacity is unnecessarily reduced.

In order to obtain high reaction rates, the sulfuric acid should bethoroughly mixed with the hydrocarbons present. The circulation rateshould be such that the desired degree of mixing is maintained forsufiicient time to allow the reaction of substantially all of the addedolefin during one cycle of flow. It is highly desirable that nosubstantial recycling of unreacted olefin takes place. The proportion ofreaction mixture diverted to cooler l2 and the degree of cooling thereinare preferably adjusted so as to maintain a temperature of about 0 C. toabout 35 (3., preferably about C. to 25 0., in time tank l8. One effectof recycling reaction mixture is to so increase the mass of liquidcirculating through the time tank that only a small temperature riseresults from the heat of reaction and of friction. Such heat can beremoved efficiently at any one point and the cooler can be of the mostefficient type and can be located in the main circulationstream insteadof in a branch thereof as shown in the drawing, the choice of locationdepending upon the flow rates most suitable for the particular coolerused.

paraffin is removed by line 29.

It is not essential to have complete separation of hydrocarbon and acidin separator II but it is highly advantageous to prevent removal of acidfrom the system with the hydrocarbon phase withdrawn through line l8.Should loss of acid occur in this or any other way, e. g. leakage,chemical reaction, etc., make up acid may be added, for example, throughvalved line 20 connecting line 19 with an acid supply not shown. It isdesirable to continuously or intermittently replace a part of the acidin the system, which may be withdrawn through valve controlled line 2i,by fresh or suitably purified acid added through line 2|], althoughperiodic draining of all the acid from the reactor and its replacementwith fresh or purified acid, may also be used. Increased amounts ofproducts boiling higher than the initial reaction product are usuallyassociated with the falling off in conversion rate which is indicativeof the desirability of replacing catalyst acid. Emulsificationdifiiculties and sulfur dioxide evolution can be overcome by replacingcatalyst acid.

The hydrocarbon phase Withdrawn from separator i I through pipe line [8is conducted by line 26 to a distillation unit 21 for recovery ofreaction product. Although it is not essential to the process of ourinvention, a part of the withdrawn hydrocarbon phase may advantageouslybe taken off by line 25 before such distillation and used to dilute theolefin-isoparaffin feed in line 3. In still 21, which may be of theflash distillation type, the higher boiling products formed in thereaction are taken off as bottoms through line 2-8 while the unreactedhydrocarbon containing iso- The unreacted hydrocarbon thus recovered maybe returned to the reaction system, preferably with the olefinic feed asby lines 3b and 32. Where inert components are present these mayadvantageously be removed before returning the isoparaffin content tomix with the olefin feed. In the drawing the removal of inert componentshaving a higher boil ing point than the isoparafiin being used in thereaction, for example the removal of normal from isobutane, isillustrated. In such a case the overhead product from still 2? is fed tostill M from which the isoparafiin is removed byline 32 and returned topipe line 3 while the inert component or components are withdrawn fromthe system by line 33. It will be obvious that depending upon theboiling points, relative solubilities, etc. of the isoparafiin and inertmaterial, other distillation methods or extraction or other suitableprocedures may be used for removal of the inert material.

The particular combination of operating conditions to be used in anyparticular case will depend upon the isoparaifin and olefin or mixturethereof to be reacted. In all cases we prefer to operate undersufficient pressure to maintain the reactants in the liquid phase. Wealso prefer to use acid concentrations which are as high as possible inorder to promote absorption of isoparaffin therein. With sulfuric acidcatalysts the upper limit of acid concentration depends upon thetemperature employed as too high a concentration of acid' at too high atemperature leads to undesirable sulfonation reactions and the like.Furning sulfuric acid at temperatures below 0 C. may be used. Thetendency of sulfuric acid catalysts to cause sulfonation may be reducedby the use of phosphoric acid. Solutizer-s for the isoparaffin beingreacted, such as benzene sulfonic acid and the like, may be usedwiththe,

aromas 7 catalyst acid as may also inorganic salts such as heavy metal.sulfates'which have a beneficial influence on the reaction. Sulfuricacid of less than about 90% concentration is preferably not used and forthe reaction of isobutane with normal butylenes, acid of about 96% to110% concentration, preferably 98% to 102%, is desirable. Temperaturesbetween 35 C. and -20 C. are suitable. With the preferred 98% 'to 102%sulfuric acid a temperature of .C. tolO .C. is advantageous, highertemperatures being applicable with weaker acid and lower temperaturesbeing desirable with more concentrated acid. The difference inreactivity of different isoparaffins does not appear to be as great asthe difference in reactivity of the various olefins. Thus where the sameolefin or olefins are used substantially the same reaction conditionsmay be successfully employed for the reaction .of isopentane therewith.as when .isobutane is used. When isobutylene is substituted it isadvisable to alter the operating conditions to compensate for the muchgreater reactivity of the tertiary olefin. We prefer, when using highlyreactive olefins to increase the ratio of isoparaiiin The followingtables show the advantageous results obtainable by the process of ourinvention as applied to the reaction of isobutane with butylenes, andthe effect of diiferent operating-conditions thereon. The reactionswerecarried out in a bronze turbo mixer of 1160 cc. capacity providedwith a cooling coil through which cold acetone was circulated at asufficient rate to maintain the desired temperature. The mixer was 10provided with inlet lines for isoparaffin-olefin feed'andreturned-acidand a draw-offline leading to a stratifier from which upper hydrocarbonphase was continuously removed while lower acid phase was taken off bythe acid return line. The

isoparaffln and olefin for reaction were continuously fed to the reactorunder a pressure of about 150 to .200 (lbs/sq. in. gauge, at a ratecontrolled bya thermo flow-meter. Hydrocarbon phase was withdrawn fromthe separator at the same rate and distilled and the reaction productand unrefor beta-butylene, for example, on the other hand,

acted hydrocarbon recovered and analyzed. In all cases the acid used ascatalyst was saturated with isobutane free from olefin before the startof the run. The effect of premixing the olefin feed with isoparaffin isshown in Table I.

.Table I Exp. No 22 Mols of isobutane added to the feed per mol ofbutylene fed. Olefin concentration of mixture fed Sulfuric acid catalystconcentration (weight per cent H28 04). Volume ratio of acidtohydrocarbon Temperature Feed rate (cc. of hydrocarbon/min.) Contact timeYield as per cent of olefin fed. Volumes of product/volume of aci lcrc2entC of product boiling between 24 (land Initially"-.. After 3 vols. ofproduct/vol. of acid After 6.75 vols. of product/vol of acid After 8.75vols. of product/vol. of acid Condition of catalyst at end of testAlmost 00 mpletely spent.

so: Substantially although still not completely spent.

ently not more than of producing about ha lf its effective life 9 morevols.- of produtlllzed. not.

to olefin used, particularly in the feed mixture to the reactor butalsoadvantageously in the reactor as well. Where propylene is used asone of the reactants due allowance must be made for its differentreactivity. When oleflnic mixtures such as are obtained in Dubbscracking processes are used the conditions should be adjustedwithparticular reference to the more reactive olefin present. Thedifferences in reactivity of secondary olefins of six or more carbonatoms per molecule are not so pronounced and-it has'been foundsatisfactory to react cracked gasoline with isobutane to obtain asaturated gasoline ofhigh anti-knock value by using conditions quitesimilar to those employed when reactingisobutane with butylenes.

Presence of alcohols, ethers, ketones, etc., which tend to split off H2Oin the presence of H2804, is undesirable because of the diluting effectof such decomposition product on the acid. Likewise nitrogen bases, suchas amines, etc. in the feed stool: are preferably avoided. We find itconvenient to use the spent catalyst acid,'preferably after dilutionwith water, e. g. to about60-to 75% or lower, to remove such undesirablecomponents from the feed stock but other suitable methods whether ofthesolventextraction-type or-not may also beemployed.

These results show .the advantage of feeding a high ratio of isoparafiinto olefin, it being apparent that doubling the ratio of isobutane tobutylene in the feed under otherwise similar conditions not only greatlyincreases th 'yield .(from 6.75 to an estimated 23 volumesof product pervolume of acid) and gives better yields (192% compared with 148% basedon the amount of olefin used) ofebetter quality products but also makesfeasible production-rates not feasible when the lower isoparaifin to.olefin ratios are used. The importance of having a high .ratio of .iso-

paraffin to olefin in the feed, is clearly brought out by a comparisonof the figures in columns one and four of Table I which are results'oftests in which the ratios of isoparaffin to olefin in the reactor wereapproximately the same, the lower 5 isoparaffin-olefin ratio in thefirst case being nearly compensated for by the lower recycle ratio ofthe latter. We consider it particularly advantageous to maintain a highconcentration, suitably at least l0% and more preferably 50% or higher,of the isoparafiin or isoparafiins being reacted, in the hydrocarbonphase of the reaction mixture.

InTable II the effect of acid concentrationand temperature onthe-reaction of isobutane with a butylene mixture containingbeta-butylene asthe predominating olefin together with smaller amountsof iso and alpha-butylene, is shown.

primary reaction product in the reaction. mixture which makes possiblehigher yields of such de- Table II Exp. No 29 Mol oi isohutanc added tothe feed per mol of burylcne fed. Olefin concentration of mixture fedSulfuric acid catalys conc.(weight per cent Has 04) Volume ratio of acidto hydrocarbon 0 Temperature Feed rate (cc. of hydrocarbon/min.) Contacttime, min Yield as per cent of olefin fed.. Volumes of product/volume ofl Per c crt of product boiling between 24 C. and

Initially After 3 vols. of prod/v l. of acidv After 6.75 ls. oiprod/vol. of acid" gm? 8.75 vols. of prodJvol. of acid .nr Condition ofcatalyst at end of test.

Spent...

Spent-..

16:7--. Spent...

Still active" Still active.

St' active.

These results bring out the desirability of using strong acid andsuppressing sulfonation by operating at low temperatures. They also showthe extremely long life of the catalyst when our method of operation isemployed. The high production rates obtainable by our process are shown;for example, by the test reported in the last column of Table I, wherethe rate of production of higher boiling hydrocarbon was 1.01 volumesper hour per volume of reaction space.

It will thus be evident that our process for reacting isoparaffins witholefins offers many advantages particularly in efficiency of operationand economy of catalyst acid. It not only provides a simple method,recycling of reacted mixture, for maintaining a high ratio oflsoparalfin to olefin but also permits of thorough mixing and themaintenance of the reaction mixture in a highly dispersed condition, atwhich the rate of reaction is high, for sufiicient time to allow thereaction of the olefin to go to completion. Furthermore, the powerrequired for maintaining such dispersion may be supplied by a pump ofhigh efficiency in which the wear, which is a function of the powerlosses within the pump, is low, the power imported by the pump to thecirculating mixture being converted into dispersion effect in thereactor, e. g. at the perforated plates of the time tank, and alsoadvantageously in substantial amount at the juncture of lines 3 and 5.Our system provides ready control of the volumetric ratio of catalystacid and hydrocarbon phases, since by the removal of product from thesystem without removing acid a definite constant quantity of the latteris maintained in the system. In this way operation in the preferredrange of continuous hydrocarbon phase where greater opportunity fordiifusion of reactants exists is readily maintained. In our preferredform of reaction system the feed inlet and product outlet points areseparated by time tank elements or pipe coils or the like, the feed mostpreferably entering the recycle stream directly after sirable productsby reducing the opportunity for further reaction between the product andmore olefin. All of these factors contribute to make our new processhighly efiicient and economical and make its products superior inquality.

While we have described our. invention in a detailed manner andillustrated suitable means of carrying it out it will be understood thatvariationsmay be made not only in regard to the isoparaffins and olefinswhich may be reacted and the catalyst acid used therewith but also withrespect to the details of operation used. For example, while addition ofisoparaffin to the olefinic feedhas been described as ourpreferredmethod of operation, it is also possible to make such addition to thereaction mixture separately soas to maintain therein the desired highconcentration of isoparaifin. Also, instead of using the process for theprimary production of relativelylow boiling isoparafiins by reaction ofone molecule of olefin with one molecule of isoparafiin, higher boilingproducts may be prepared by maintaining such a high concentration ofsuch primary products in the mixture. that their further reaction withanother molecule of olefin is promoted. While, emphasis has been placedon our preferred method of continuous operation it willbe obvious thatmany features of our invention are also highly advantageous whenoperating intermittently or batch-wise. Again where return of unreactedhydrocarbon containing normal paraffinssubstantially inert under theconditions of our reaction has been described, it will be understoodthat in many cases such compounds can be advantageously isomerized, forexample by passing their vapors over aluminum chloride catalyst at anelevatedtemperature, either after separation of such compounds in still3l or not, before such return to the system, and the resultingisoparaffins used in our process. Still other modifications may be madein the process of our invention; consequently no limitations other thanthose imposed by the scope of the appended claims are intended.

This application is a division of our copending application Serial No.245.714, filed December 14, 1938, now Patent No. 2,435,402.

We claim as our invention:

1. Process of manufacturing high anti-knock motor fuel constituentsboiling in the aviation gasoline boiling range from cracking still gasescontaining a mixture of isoparaifin, normal paraffin, and olefin, whichcomprises charging said gaseous mixture to a reaction zone whereinisopar'afiin is alkylated with olefinby contact with an alkylationcatalyst comprising sulfuric acid of alkylating concentration,simultaneously maintaining the concentration of isoparaffin to bealkylated in the hydrocarbon phase of said reaction zone above 50% byliquid volume of the hydrocarbons, maintaining the ratio of isoparaffinto olefin at the point where the olefin initially contacts the catalystabove 100 to 1', and maintaining a high degree of contact between theacid and hydrocarbon phases to produce a highyield of high anti-knockmotor fuel hydrocarbons boiling in the aviation gasoline boiling range.

2. Process of manufacturing high anti-knock .zone above 50% by liquidvolume of the hydrocarbons, maintaining the ratio of isobutane to buteneat the point where the butene initially contacts the acid catalyst above100 to 1, and maintaining a high degree of contact between the acid andhydrocarbon phases to produce a hi h yield ofhigh anti-knock motor fuelhydrocarbons boiling in the aviation gasoline boiling range.

3. In a processof manufacturing high antiknock motor fuelconstituentsboiling in the aviation gasoline boiling range from cracking. stillgases comprising a, mixture of isoparafiin, normal parafiin and olefin,wherein said mixture is charged to a reaction zone in which the isopareaffin is a kylated with said olefin by contact with an alkylationcatalyst comprising sulfuric acid of alkyl'ating concentrationwhilemaintainin the ratio of said isoparaffin to olefin at least 50 to 1at the point where the olefin initially contacts the catalystand'maintaining a high degree of contact between the acid andhydrocarbon phases, the improvement which comprises simultaneouslymaintaining the concentration of the isoparafiin to be alkylated in thehydrocarbon phase of said reaction zone above 60% by liquid volume ofthe hydrocarbons to produce a high yield of high anti-knock motor fuelhydrocarbons boiling in the aviation gasoline boiling range.

4. In a process of manufacturing high antiknock. motor fuel constituentsboiling in the aviation gasoline boiling range from isobutane andbutene, wherein a mixture of isobutane, normal butane and butene iscontacted with an alkylation. catalyst comprising sulfuric acid underalkylationconditions while maintaining the ratio of. isobutane to buteneat the point where the butene initially contacts the acid catalyst atleast 50-to 1. and maintaining a high deg-ree of contact between theacid and hydrocarbon phases, the improvement which comprisessimultaneously maintaining the concentration of isobutane in thehydrocarbon phase in the reaction above 60% by liquid volume of thehydrocarbons.

5.- In a process of alkylating an isoparafiin with '12 anolefin in thepresence of an alkylation catalyst acid comprising sulfuric acid ofalkylation concentration wherein the alkyl acid sulfate concentration inthe catalyst is maintained sufliciently low to produce a high qualityproduct by effecting a sufficiently high degree of mixing of hydrocarbonand acid catalyst phases, thus producing a suificiently large surface ofcontact between said hydrocarbon and acid catalyst phases whilesimultaneously maintaining the molecular ratio of isoparaflin to bealkylated to olefin at the point where olefin initially contacts theacid catalyst above IOO-to l, the improvement which comprisesmaintaining the concentration of the isoparaf'fin to be alkylated in thehydrocarbon phase of said reaction zone above 60% by liquid volume ofthe hydrocarbons.

6. In a process of alkylating isobutane with butene by means of analkylation catalyst acid comprising sulfuric acid of alkylationconcentration wherein the butyl acid sulfate concen tration in thecatalyst is maintainedsufiiciently low to produce a high quality productby effecting a sufliciently high degree of mixing of hydrocarbon' andacid catalyst phases,v thus producing a s'ufiiciently large surface ofcontact between said hydrocarbon and acid catalyst phases whilesimultaneously maintaining the molecular p ratio of isobutane to buteneat least 50 to 1 at the 'point where the butene initially contacts theacid catalyst, the improvement which comprises maintaining theconcentration of isobutane in the hydrocarbon phase in the reaction zoneabove 60% by liquid volume of the hydrocarbons.

7. In a process of alkylating an isoparaflin with an olefin in thepresence of an alkylation catalyst acid wherein a mixture of isoparafhn,normal paraflin and olefin of at least three carbon atoms per moleculeis charged to a reaction zone in which isoparaffin is alkylated witholefin by contact with said catalyst acid while maintaining the ratio ofsaid isoparafiin to olefin at the point where the olefin initiallycontacts the catalyst above to 1 and maintaining a high degree ofcontact between the acid and hydrocarbon phases, the improvement whichcomprises simultaneously maintaining the concentration of theisoparaffin to be alkylated in the hydrocarbonphase of said reactionzone above 50% by liquid volume of the hydrocarbons.

8. In a process of alkylating isobutane. with a butene wherein a mixturecomprisin isobutane, normal butane and a butene is contacted with analkylation catalyst acid under alkylation conditions while maintainingthe ratio of isobutane to butene at the point where the butene initiallycontacts the acid catalyst at least 50 to 1 and maintaining a highdegree of contact between the acid and hydrocarbon phases, theimprovement which comprises simultaneously maintaining the concentrationof the isoparaflin to be alkylated in the hydrocarbon phase of saidreaction zone above 50% by liquid volume of the hydrocarbons.

SUMNER H. McALLISTER. EDWIN F. BULLARD.

No references cited.

1. PROCESS OF MANUFACTURING HIGH ANTI-KNOCK MOTOR FUEL CONSTITUENTSBOILING IN THE AVIATION GASOLINE BOILING RANGE FROM CRACKING STILL GASESCONTAINING A MIXTURE OF ISOPARAFFIN, NORMAL PARAFFIN, AND OLEFIN, WHICHCOMPRISES CHARGING SAID GASEOUS MIXTURE TO A REACTION ZONE WHEREINISOPARAFFIN IS ALKYLATED WITH OLEFIN BY CONTACT WITH AN ALKYLATIONCATALYST COMPRISING SULFURIC ACID OF ALKYLATING CONCENTRATION,SIMULTANEOUSLY MAINTAINING THE CONCENTRATION OF ISOPARAFFIN TO BEALKYLATED IN THE HYDROCARBON PHASE OF SAID REACTION ZONE ABOVE 50% BYLIQUID VOLUME OF THE HYDROCARBONS, MAINTAINING THE RATIO OF ISOPARAFFINTO OLEFIN AT THE POINT WHERE THE OLEFIN INITIALLY CONTACT THE CATALYSTABOVE 100 TO 1, AND MAINTAINING A HIGH DEGREE OF CONTACT BETWEEN THEACID AND HYDROCARBON PHASES TO PRODUCE A HIGH YIELD OF HIGH ANTI-KNOCKMOTOR FUEL HYDROCARBONS BOILING IN THE AVIATION GASOLINE BOILING RANGE.